Electrostatic coating apparatus



Sept. 1, 1964 c. c. SIMMONS ELEcTRosTATIc coATING APPARATUS Original Filed June l, 1953 United States Patent O 3,147,145 ELECTRUSTATiC CATING APPARATUS Charles Curtis Simmons, Skokie, lil., assigner to Ransburg Electro-Coating Corp., a corporation of Indiana @riginal application .lune 1, 1953, Ser. No. 358,846. Divided and this application Get. 16, 1958, Ser. No.

8 Claims. (Cl. 118-624) This invention relates to the spray coating of articles and more particularly to coating apparatus and coating methods to be used in electrostatic coating systems. This application is a division of my pending application Serial No. 358,846, filed June l, 1953, and now abandoned.

In a majority of electrostatic coating systems a field of electrostatic force is created which includes the article being coated and atomized coating material particles to attract the particles for deposition on the article. Such deposition of the atomized particles is primarily the result of electrostatic forces and for this purpose the atomized spray particles are given an electrostatic charge at the time they leave the atomizing or spraying device or shortly thereafter. Where the articles to be coated are of conducting material, it is the normal commercial practice to support the articles on a grounded conveyor and thus make the yarticles themselves one of the electrodes of the electrostatic field and at ground potential. Another electrode at high electrical potential is provided, with this latter electrode sometimes being the atomizing device and sometimes being a separate electrode near or past which the -atomized particles pass in their movement toward the article.

In United States Patent No. 2,808,343, issued October 1, 1957, there are disclosed and claimed atomizing devices mounted for rotation about an axis and means are provided for supplying liquid coating material to a surface of the device while rotating the device -to flow the material to the edge of the device for atomization therefrom. In said U.S. Patent No. 2,808,343 the device is maintained at a high electrical potential and the articles are carried on a grounded support in a path which passes through the annular spray pattern formed by the atomizer. As disclosed in the aforesaid patent, means may be provided for reciprocating the atomizing device vertically as the articles are carried in a normally horizontal, curved path around the atomizer so as to apply coating material from top to bottom of the articles, and if the articles are to be coated over their entire exterior surface the same may be rotated during their movement in said path so that coating is applied completely therearound.

In utilizing the coating apparatus described in U.S. Patent No. 2,808,343 for the spray coating of certain articles, it has been found that occasions arise where the bottom, and sometimes the top, of the article does not receive the fully desired coating, `the spray particles apparently passing under the article and depositing on its support rather than on the bottom.

It has been discovered that it is possible to secure a more uniform coating on areas such as the top and bottom of articles of the type just described by providing a deilecting electrode remote from the atomizing device but positioned adjacent the path of movement of the atomized yparticles as they move from the atomizing device toward the article, with such deliecting electrode being charged similarly as the particles. As like electrical charges create a repelling force, the deliecting electrode serves to repel the particles and thus move them out of an undesired path and into a desired path of movement so that they may deposit, for example, on the bottom of the article rather than on the article support or, again, so that the particles may be, by the electrostatic repelling forces created, directed downwardly onto the top of an article or upwardly onto the bottom.

The deflecting electrode is preferably maintained at the same electrical potential as the particle charging electrode and thus, in the embodiment hereafter to be more fully described, the deflecting electrode is maintained at the same electrical potential as the disk atomizer. Modification of the repelling effect on charged spray particles by the delecting electrode may of course be obtained by modifying or varying the potential of the detlecting electrode.

The deiiecting electrode may take the form of a circular plate stationarily, but adjustably, positioned below the rotating disk, with its edge being curved to be concentric with the center of curvature of the path of movement `of the article or articles as they pass by the atomizing device; or the electrode may be mounted above the disk and, inasmuch as the latter may be reciprocated vertically, be carried by the same means carrying the disk so as to be moved therewith during coating deposition.

Other features and advantages of the invention will be readily apparent from the following description and drawings, in which:

FIG. 1 is a top plan View, somewhat schematic in character, showing the general arrangement of the conveying device for conveying the articles to be coated around each of two atomizing devices;

FIG. 2 is a side elevational View of the electrostatic coating system of this invention;

FIG. 3 is an enlarged detailed isometric view of the atomizing device with a deecting electrode positioned therebelow; and

FIG. 4 is a view like FIG. 3 wherein the deflecting electrode is positioned above the atomizing device.

FIG. 5 is a view, similar to FIGS. 3 and 4, showing the structures thereof combined.

While this invention is susceptible of embodiments in many different forms, there are shown in the drawing and will herein be described in detail several embodiments, with the understanding that the present disclosure is to be considered as an exemplication of the principles of the invention and is not intended to limit the invention to the embodiments illustrated. The scope of the invention will be pointed out in the appended claims.

Referring now to the drawing, there is provided a conveyor 10 supported on a plurality of posts 11 of conducting material which serve to ground the conveyor as indicated at 12. The conveyor is provided with a plurality of conducting article supports 13 for carrying a plurality of articles 14 to be coated.

The articles are carried by the conveyor around an atomizing device, generally indicated yat 15, which may comprise a circular disk 16 of conducting material lixed to one end of a shaft 1'7 rotatably carried in a sleeve 18 fixed to a collar 19 mounted on an insulating crossbar 20. The sleeve 18 extends upwardly through a second insulating crossbar 21 land the other end of the shaft 17 extends beyond the upper end of the sleeve and has fixed thereto a drive pulley 22. The pulley carries an endless belt 23 which passes around a second drive pulley 22' associated with a second atomizer 15. e

As the apparatus `associated with each of the atomizers 15 and 15 are substantially similar, identical reference numerals will be used but with those `associated with the atomizer 15 being primed.

The crossbars 20 and 21 are reciprocably mounted on a vertical support 25 and means generally indicated at 26 and including the piston and cylinder device 27 are provided for reciprocating the crossbars and hence the atomizers 15 and 15 vertically during coating deposition. Such reciprocating means are further described in previously mentioned U.S. Patent No. 2,808,343.

For rotating the shafts 17 and 17 there is provided an electric motor 30 carrying a pulley 31 on its drive shaft and `an endless belt 32 passes around the pulley 31 and a second pulley 33 fixed to the shaft 17 so that operation of the motor 30 serves to rotate the shafts.

Coating material is fed to the upper surface of each of the disks and for this purpose there is provided a exible hose 34 of non-conducting material fixed by clamps to the sleeve 18 and connected at one end to a pump 35 for supplying coating material under pressure through the hose. Coating material fed to the upper surface of the disk ows to the edge thereof by the action of centrifugal force with rotation of the disks.

Both of the disks 16 and 16 are maintained at a high electrical potential and for this purpose are connected to a source of such potential by means of the wires 35 and 36,'. The Wire 36 is in electrical contact with the metal collar 19 and thus charges the disk 16 through the metal sleeve 18 and shaft 17.

In operation, coating material fed to the upper surface of the disk 16 in the manner previously described flows to the edge thereof and is atomized. Because of the fact that the disk 16 is maintained at a high electrical potential relative to ground, the atomized particles are given an electrostatic charge and thus are moved by electrostatic forces toward and deposited upon the articles 14. Means (not shown) are associated with the conveyor for rotating the articles as they pass around the atomizing devices and during such passage the atomizers are reciprocated vertically so as to -apply coating material over the entire exterior surface of the articles. The spray of charged particles issuing from the atomizing devices is annular in shape and the path of movement of the articles conforms to the annular spray pattern thus formed so that the articles pass through the spray of charged particles.

As previously noted, with some articles difficulty is encountered in securing a proper coating on the bottom or on the top of such articles. Thus, for example, the spray issuing from the atomizer when the same is in its lowest position shown in FIG. 2 may have a tendency to deposit on the supports 13 rather than on the bottom of the articles 14. To provide for a better coating on the bottom of the articles there is provided a deflecting electrode, generally indicated at 37, which, as previously indicated, may carry a charge like in sign to the charge of the particles and thus act to repel the particles. Such repelling force is utilized to cause the charged particles to move in paths other than the paths they would have moved in in the absence of the electrode to provide for a better distribution of coating material.

The defiecting electrode 37 may take the form of a circular plate 40 mounted on a metal rod 41 slidable in an insulating support 4Z and securable thereto in any one of a number of adjusted positions by means of a set screw 43. The rods 41 and 41 may he connected to the source of high potential through the wires 44 and 4'4 as shown.

The deflecting electrode is so positioned as to create an electrostatic repelling force on charged particles which are traveling toward the supports 13 and thus electrostatically to deflect them upwardly toward and cause them to deposit upon the bottoms of the articles 14.

Where diculty is encountered in applying coating to the tops of the articles, the deecting electrode may take the form shown in FIG. 4. As shown in that figure the deecting electrode 45 comprises a metal band 46 curved to a circular form and provided with an integral tab portion 47 secured to a metal sleeve 18a rotatably supporting a shaft 17a, which shaft carries an atomizing disk 16a similar to the disk, shaft and sleeve 16-18 previously described. Coating material is supplied to the upper surface of the disk 16a through a flexible hose 34a of insulating material which serves the same purpose as the hose 34. In this latter form of deflecting electrode the electrode itself is reciprocated with the disk and thus main- A tains its position spaced from the disk during coating operation.

It will be noted that the defiecting electrodes shown in FIGS. 3 and 4 are positioned adjacent the path of par; ticle movement as they move from the atomizer toward the article and each serves electrostatically to alter or determine the path of movement `taken by the charged particles and thus the point of deposition. By proper positioning of the deflecting electrodes, particles which might otherwise deposit on the supports for the article or on areas other than desired, for example other than the top or bottom of the article, may have their paths of movement altered by the electrostatic forces created so as to cause the particles to deposit on desired areas of the article. Obviously, if the situation so requires it, the deflector of FIG. 3 can be used in conjunction with the defiector of FIG. 4 electrostatically to deflect the atomized particles into a desired path of movement. Such an arrangement is shown in FIG. 5, wherein corresponding parts have been given the same reference numerals with the suffix b.

I claim:

l. In an electrostatic coating arrangement comprising a circular-edged atomizer mounted for rotation about a substantially Vertical axis, means for feeding liquid coating material to the atomizer, means for rotating the atomizer to flow the coating material to the outer edge thereof for atomization therefrom as a spray of finely divided particles, a grounded conveyor lying in a generally hori- Zontal plane and a plurality of supports each having an article supporting portion spaced perpendicularly from said conveyor each supporting an article for moving the articles in a generally horizontal, curved path surrounding the atomizer and spaced vertically from the conveyor, a source of high voltage connected to the atomizer to create a high electrostatic potential between the atomizer and the surrounding grounded articles electrostatically to deposit the particles on the articles as a coating, and means for reciprocating the atomizer generally along said vertical axis between limits generally defined as between the upper and lower portions of the articles being coated, the improvement comprising a deflecting member, means independent of the reciprocating atomizer for supporting the deflecting member in a fixed position spaced axially from said atomizer and on the same side thereof as the conveyor and between the atomizer and the conveyor, said deflecting member supporting means positioning the deflecting member beyond the limits of atomizer reciprocation, and means for connecting said defiecting member to said high voltage source for maintaining said deflecting member at substantially the same potential as said atomizer to inhibit the deposition of spray particles onto the supports and the conveyor.

2. Apparatus according to claim 1 in which the deflecting member has an outer edge substantially concentric with and parallel to the outer edge of the atomizer.

3. Apparatus according to claim l in which the deflecting member is a metal member having an outer diameter substantially the same as that of the atomizer.

4. An electrostatic coating arrangement comprising a rotatable atomizer mounted for rotation about a substantially vertical axis, means for feeding liquid coating material to the atomizer, means for rotating the atomizer to ow coating material to the atomizing zone thereof for atomization therefrom in a substantially annular pattern, a grounded conveyor located below the articles for moving articles in a curved path to position the articles in a coating zone substantially surrounding the atomizer, means for vertically reciprocating the atomizer, a circular detiecting member independently mounted in fixed position below said atomizer and between the atomizer and the conveyor, a source of high electrical potential, means for connecting said source to the atomizer to create an electrostatic charge differential between the atomized particles and the article electrostatically to move the particles toward and deposit them on articles in said coating zone, and means for connecting the deecting member to said source of high potential to inhibit the deposition of atomized particles onto the conveyor.

5. An electrostatic sprayer comprising a rotary spraying member having a sharp peripheral edge, means for supplying coating material to said member to be discharged thereby, a pair of preshaped electrodes spaced respectively above and below said rotary spraying member, one of said pair being positioned each with its plane disposed on an opposite side of said spraying member, electrical means for creating an electrostatic iield between said spraying member and an object to be coated, said preshaped electrodes being positioned relative to said spraying member and electrically connected to act as repelling electrodes for said coating material.

6. An electrostatic sprayer comprising a rotary spraying member having a peripheral edge, means for supplying coating material to said member to be discharged thereby, a pair of preshaped electrodes spaced respectively above and below said rotary spraying member, one of said pair being positioned each with its plane disposed on an opposite side of said spraying member, electrical means for creating an electrostatic field between said spraying member and an object to be coated, said preshaped electrodes being positioned relative to said spraying member and electrically connected to act as repelling electrodes for said coating material.

7. An electrostatic coating arrangement comprising a reciprocable atomizer for forming a spray of coating material particles, a grounded conveyor for moving an article to be coated in a path passing through said spray, means for reciprocating the atomizer toward and away from the conveyor, a source of high electrical potential, means for connecting said source to the atomizer to create an electrostatic charge differential between the atomizer and the article electrostatically to move the spray particles toward and deposit them on the article, a stationary deflecting member approached by the atomizer as the atomizer moves toward the conveyor, means for mounting the deecting member adjacent the path of spray particle movement and between the atomizer and the conveyor to be approached by the atomizer as the atomizer moves toward the conveyor, and means for electrostatically charging the deflecting member to substantially the same potential as said atomizer, said deecting member being automatically operable for varying the electrostatic repelling force between the charged delecting member and the spray particles as the atomizer approaches the conveyor in its movement.

8. An electrostatic coating arrangement comprising a reciprocable atomizer for forming a spray of coating material particles, a grounded conveyor for moving an article to be coated in a path passing through said spray, means for reciprocating the atomizer toward and away from the conveyor, means for creating an electrostatic charge diierential between the spray particles atomized from the atomizer and the article electrostatically to iove the particles toward and deposit them on the article, a stationary deecting member approached by the atomizer as the atomizer moves toward the conveyor, means for mounting the deiiecting member adjacent the path of spray particle movement toward the article and between the atomizer and the conveyor to be approached by the atomizer as the atomizer moves toward the conveyor, and means for electrically charging the deecting member, said deflecting member being automatically operable for Varying the electrostatic force between the charged deilecting member and the spray particles as the atomizer approaches the conveyor in its movement.

References Cited in the le of this patent UNITED STATES PATENTS 2,651,287 Turner Sept. 8, 1953 2,658,009 Ransburg Nov. 3, 1953 2,711,155 Starkey `lune 21, 1955 2,754,226 .Tuvinall July 10, 1956 2,773,472 Lamm Dec. 11, 1956 2,780,565 Juvinall Feb. 5, 1957 2,808,343 Simmons Oct. l, 1957 

1. IN AN ELECTROSTATIC COATING ARRANGEMENT COMPRISING A CIRCULAR-EDGED ATOMIZER MOUNTED FOR ROTATION ABOUT A SUBSTANTIALLY VERTICAL AXIS, MEANS FOR FEEDING LIQUID COATING MATERIAL TO THE ATOMIZER, MEANS FOR ROTATING THE ATOMIZER TO FLOW THE COATING MATERIAL TO THE OUTER EDGE THEREOF FOR ATOMIZATION THEREFROM AS A SPRAY OF FINELY DIVIDED PARTICLES, A GROUNDED CONVEYOR LYING IN A GENERALLY HORIZONTAL PLANE AND A PLURALITY OF SUPPORTS EACH HAVING AN ARTICLE SUPPORTING PORTION SPACED PERPENDICULARLY FROM SAID CONVEYOR EACH SUPPORTING AN ARTICLE FOR MOVING THE ARTICLES IN A GENERALLY HORIZONTAL, CURVED PATH SURROUNDING THE ATOMIZER AND SPACED VERTICALLY FROM THE CONVEYOR, A SOURCE OF HIGH VOLTAGE CONNECTED TO THE ATOMIZER TO CREATE A HIGH ELECTROSTATIC POTENTIAL BETWEEN THE ATOMIZER AND THE SURROUNDING GROUNDED ARTICLES ELECTROSTATICALLY TO DEPOSIT THE PARTICLES ON THE ARTICLES AS A COATING, AND MEANS FOR RECIPROCATING THE ATOMIZER GENERALLY ALONG SAID VERTICAL AXIS BETWEEN LIMITS GENERALLY DEFINED AS BETWEEN THE UPPER AND LOWER PORTIONS OF THE ARTICLES BEING COATED, THE IMPROVEMENT COMPRISING A DEFLECTING MEMBER, MEANS INDEPENDENT OF THE RECIPROCATING ATOMIZER FOR SUPPORTING THE DEFLECTING MEMBER IN A FIXED POSITION SPACED AXIALLY FROM SAID ATOMIZER AND ON THE SAME SIDE THEREOF AS THE CONVEYOR AND BETWEEN THE ATOMIZER AND THE CONVEYOR, SAID DEFLECTING MEMBER BEYOND THE LIMITS OF ATOMIZER RECIPROCATON, AND MEANS FOR CONNECTING SAID DEFLECTING MEMBER TO SAID HIGH VOLTAGE SOURCE FOR MAINTAINING SAID DEFLECTING MEMBER AT SUBSTANTIALLY THE SAME POTENTIAL AS SAID ATOMIZER TO INHIBIT THE DEPOSITION OF SPRAY PARTICLES ONTO THE SUPPORTS AND THE CONVEYOR. 